Electrical apparatus



Jan. 29, 1952 J. D. KRAUS 2,583,953

ELECTRICAL APPARATUS Filed March 29, 1946 INVENTOR; JOHN D. KRAUS.

ATTORNEY Patented Jan. 29, 1952 ELECTRICAL APPARATUS John D. Kraus, Newton Center, Mass, assignor to United States of America as represented by the Secretary of War;

Application March 29, 1946, Serial No. 657,949

Claims. (01. 250-33.65)

This invention relates generally to electricalap paratus and more particularly to antennas.

Often it is desirable to use a unidirectional antenna, particularly in direction finding systems.

Directional antennas are certainly not an unusual type, however when additional performance re-" quirements of such an antenna are specified, a compromise on each individual requirement is usually made with the idea of obtaining a resultant antenna which has several characteristics, each of a satisfactory value rather than of optimum value. For example a particular antenna may be required to have a unidirectional pattern and also to be a broad band antenna.

It is an object of the present invention to provide an antenna particularly adapted for use in a direction finding system.

It is also an object to provide a unidirectional antenna for operation over a wide range of frequencies.

It is another object to provide a broad band antenna-reflector combination having a unidirectional pattern.

It is a further object to provide an antenna a system which is balanced with respect to ground to a system which is unbalanced with respect to ground.

An example of an antenna which accomplishes 1 adapted to be fed by an unbalanced line, such as a coaxial cable without the use of a so-called; "balun which is usually required for connecting sembly.

v in parallel.

is substantially in the form of a W. Such an invention will suggest themselves to those skilled H in the art and will become apparent from the following description of the invention taken in connection with the accompanying drawing in tenna and a W-reflector assembly. This assemblyfis shown fed by a balanced transmission line system consisting of coaxial transmission lines to and II. The ends of the outer conductors of coaxia1 transmission lines It and I! are flared and terminate in contact with sheet reflector I2, as shown at IDA and HA. The inner conductors of coaxial trasmission lines I0 and II are flared as shown at I03 and I IB and terminate in contact with the ends of the antenna radiating elements I3 and I4 respectively. Radiating elements I3 and I4 are substantially cylindrical and their longitudinal axes intersect to form a Vat an angle whose value isidentical with the angle 9 formed by the inner legs of sheet reflector I2. The ends of radiatingelements I3 and. I 4 which form the apex of a V do not make cnntact with each other but are separated a small. distance. In practice, the apex may be either closed, or open as shown in the drawing. The latter condition is slightly better when wide band operation is desired. Arrow I5 indicates the direction. of maximum response of the antenna-reflector as- Figs. 1A and 1B are two views of the same apparatus, hence the reference numbers of Fig. 1A are repeated in Fig. 1B. A I

A modification of the antenna system of Fig. 1A is shown in Fig. 2 wherein the two radiating elements 23 and 24 are made integral where they intersect to form the apex of a V. Although two feed lines 2!! and 2| are shown, this arrangement is adapted to be energized byan unbalanced line such as 25, since lines 2|] and 2| are connected One end of line 20 has its outer conductor terminated by flaring it as shown at 23A and connected to reflector 22. Similarly the inner conductor is flared as shown at 23B and connected to radiating element 23. A portion of line 2! is contained by the, full length of radiating element 24 and at an end of element 24, the outer conductor of line 2I is flared as shown at 2IA and is connected to element 24. Where the inner conductor of line 2| leaves the confinement of element 24, it is flared as shown at 2IB and terminates in contact with sheet reflector 22. To provide proper phasing of the currents in radiating elements 23 and 24, the length of each feed line 20 and ZI from the feed points at the ends of elements 23 and 24 to the junction point of lines 20, 2| and 26, should be the same.

A second modification of the apparatus of Fig. 1A is shown in Fig. 3. Here again, the major parts of the assembly consists of two cylindrical radiating elements 33 and 34, and a sheet reflector 32, Enclosed concentrically in radiating eleaxial line 3! is also connected to line 36.

ment 3% is a' portion of coaxial line 3!, whose outer conductor is flared as shown at 51A and terminates in contact with an end of radiating element 35. The inner'conductor of line 3! extends out of radiating element 34 and is flared is an impedance balancing conductor-e? which-is connected to the end of the inside of element '33 adjacent to point 363. The other end of com ductor 37 is connected to the outer conductor of line 3 I In antenna assemblies of the type disclosed in this invention, theangle (Fig. 1) formed by the inner legs of the W-reflector and the angle formed by the radiating elements is not critical but should be of the order of 100 degrees.

The other. endv of line 3! is connected to the possible due to the particular design of these two antennas which eliminates the necessity of a balun. 7

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to. those skilled in the art that various changes and modifloations may be made therein without depart ing from the scope of the invention.

What is-claimed is: I 1. A broad band unidirectional end fed dipole V-antenna including a sheet reflector bent in theform of a w, a thick tubular first radiat' ing element oriented parallel to a first inner leg -.of said reflector, a first coaxial transmission line inserted through a hole in a first outer leg of said reflector-with its outer conductor flared and bent As'ln all antenna systems, the problem of ,im-

pedance matching is encountered, consequently the ended the inner and outer conductors of the coaxial feed lines are tapered at points where impedance transformation is required.

To obtain a unidirectional, broadband antenna of the type shown in the drawings, several well known principles have been utilized. A .broad band characteristic has .been obtained by .the .use of thick radiating elements. Directional characteristics have been obtained by' orienting the radiating elements with respect to each other to form .a V, and the value of the angle thus' formed is chosen such that the two patterns of the two radiating elements reinforce each other ,alonga line bisecting the V and tend to cancel each other in all other directions. can be made generally unidirectional, however a sheet reflector bent in theform of a W has been used in this invention to further increase the front to back ratio and to increase the gain of the antenna.

Generally, V-antennas have a length which is long compared to a wavelength, however such is not a requirement in the antenna systems herein disclosed. This reduction in required physical length is due to the fact that radiation from a thick element is greater per unit length; than from a thin element. Thus, two advantages are gained by using radiating elements of large diameters; the effective Q is lowered permitting broad band operation and the required physical length is reduced.

The frequency range over which the pattern of the antenna shown in Fig. lis'satisfactory for use in direction finding systems, corresponds to frequencies for which the length L shown in' Fig.

;1B is between approximately two-tenths wavelength and three wavelengths. Over a some- ;what ,narrower frequency range, modifications of the antenna of Fig. v1 as shown in Figs;2 and 3 are also satisfactory for use with direction flnding systems Obviously the antenna shown in Figs. 1A and 1B is de gn d to b edby atwo wire line which a is balanced with respect to ground. The antennfi Shown n Fi s. 2 and 3 are shown connected directly to an unbalanced line without the use of a balun previously referred to in th object of this invention. Such a connection is A V-antenna backward terminating incontact with said reflector and its inner conductor flared and terv'minat'ing in contact with an end of said first radiating element, a tubular second radiating element having a large diameter compared to its. length oriented parallel to a second inner leg of said reflector, a second coaxial transmission line inserted through a hole in a second outer leg ofsaid reflector with its outer'conductor flared and bent backward terminating in contact with .said reflector and its inner conductor flared and terminating'in contactwith an end of saidsecond radiating element'whereby the direction of maximum response of said 'antenna'is in a direction of the apex of a V formed by 'the intersection of the longitudinal axes said radiating elements. v

2. A 'broad band unidirectional end fed V-antenna including a sheet reflector bent to 'form four legs in the shape of a W having two outer legs and two inner legs, a thick tubular radiating elementbent to form two legs in the shapeof a V oriented with respect to said-reflector so that the inner legs of said reflector are parallel to corresponding'legs of said radiating element, a first coaxial transmission line inserted through a .hole in ,a first outer leg of said reflector with @its outer conductor flared and bent'backward terminating in contact with said reflector and its inner conductor flared and terminating in contactwith an end of a first half of said'radiating element, a second coaxial transmission line a portion of which is contained concentrically within a second half of said radiating elementv With'its outer conductor flared and bent. backward terminating in contact .with an end of Saidsecond half of said radiating element and its inner conductor flared terminating in contact with .a second outer leg of saidreflector, a third coaxial transmission line connected in parallel element. 1

3. Abroad band unidirectional end fed dipole f V-antenna including a sheet reflector bent to with an end of each of said-first and said second coaxial transmission'lines whereby the direction of maximum response of said antenna is in the direction ofthe apex formed by said radiating form four legs in the shape of a W having two outer legs and :two inner legs, a first thick radiating element oriented parallel to a first inner leg of said reflector, a first coaxial transmission line withits outer conductor terminatingin contact with said reflector and its inner conductor flared and terminating :in contact with an end of'said first radiating element, a second radiating element with a large diameter compared to its length oriented parallel .to a second inner leg of said reflector, a second coaxial transmission 4 line a portion of which is contained concentrically within said second radiating element with its outer conductor flared and bent backward terminating in contact with an end of said second radiating element and its inner conductor flared and terminating in oontactwith a second .outer leg of said reflector, a third coaxial transmission line connected in parallel with an end of each of saidflrst and said second coaxial transmission lines whereby the direction of maximum response of said antenna is in the direction of the apex formed by the intersection of the axes of said radiating elements.

4. A broad band end-connected V-antenna in cluding two thick tubular radiators whose longitudinal axesintersect to form a V, a reflector bent to form four legs in the shape of a W having two outer legs and twoinner legs oriented behind said radiators on the side'of the included angle of the radiators with said inner legs of said reflector parallel to said radiators, and a coaxial transmission line divided into two parallel elec tric'al-branches, one of said branches being connected to one of said radiators and the other of said branches being connected to the other of said radiators.

5. A broad band antenna including an endconnected V-antenna, a reflector bent to form four legs in the form of a W having two outer legs and two inner legs located near the side of the included angle of said V-antenna with said inner legs substantially parallel to said V-antenna and a feed line comprising a coaxial transmission line which divides into two parallel branches with the inner conductor of one of said branches connected to one end of said antenna and with the outer conductor of the other of said branches connected to the other end of said V-antenna.

6. A broad band undirectional end fed V-antenna including a sheet reflector bent to form four legs in the form of a W having two outer legs two inner legs, a thick tubular radiating element bent to form two legs in the shape of a V spaced from and oriented with respect to said reflector so that the inner legs of said reflector are parallel to corresponding legs of said radiating element, a first transmission line having one conductor thereof terminating in contact with a first end of said radiating element and having a second conductor thereof terminating in contact with said reflector at a point adjacent said first end of said radiating element, and a second transmission line having one conductor thereof terminating in contact with a second end of said radiating element and having a second conductor thereof terminating in contact with said reflector at a point adjacent said second end of said, radiating element.

7. A broad band unidirectional end fed V-antenna including a sheet reflector having two outer legs and two inner legs bent in the form of a W, a thick tubular radiating element bent to form two legs in the shape of a V spaced from and oriented with respect to said reflector so that the inner legs of said reflector are parallel to corresponding legs of said radiating element, a first transmission line having one conductor thereof terminating in contact with a first end or said radiating element and having a second conductor thereof terminating in contact with a first outer arm of said reflector at a point adjacent said first end of said radiating element, a second transmission line having one conductor thereof terminating in contact with a second end of said radiating element and having a second conductor thereof terminating in contact with .a second outer arm oi said reflector at a point adjacent said second end of said radiating element, and means for supplying energy to said two transmission lines irom'a common source at selected distances from their termination with said reflector and said radiating element whereby said first and second ends of said radiating elements are instantaneously of opposite polarity thereby causing the maximum response of said antenna to be along the direction of the apex of the V formed by said radiating element.

8. A broad band unidirectional end fed V -antenna including a sheet reflector bent to form four legs in the form of a W having two outer legs and two inner legs, athick tubular radiating element bent in the shape of a V oriented with respect to said reflector so that the inner legs of said reflector are parallel to corresponding legs of said radiating element, a first coaxial transmission line insertedthrough a hole in a first .outer leg of said reflector with its outer conductor terminatingin contact with said reflector and its inner conductor terminating in contact with an end of a first half of said radiating element, a second coaxial transmission line, a portion of which is contained within a second half of said radiating element with its outer conductor terminating in contact with an end of said second half of said radiating element and its inner conductor terminating in contact with a second outer leg of said reflector and means for connecting said two transmission lines in parallel to a common source whereby the direction of maximum response of said antenna is in the direction of the apex formed by said radiating element.

9. A broad band unidirectional end fed V-antenna including a sheet reflector bent to form four legs in the form of a W having two outer legs and two inner legs, a thick tubular radiating element bent to form two legs in the shape of a V spaced from and oriented with respect to said reflector so that the inner legs of said reflector are parallel to corresponding legs of said radiating element, a first coaxial transmission line inserted through a hole in a first outer leg of said reflector with its outer conductor flared and bent backward terminating in contact with said reflector and its inner conductor flared and terminating i contact with a first end of said radiating element, and a second coaxial transmission line inserted through a hole in a second outer leg of said reflector with its outer conductor flared and bent backwards terminating in contact with said reflector and its inner conductor flared and terminating in contact with a second end of said radiating element whereby the direction of maximum response of said antenna is in a direction of the apex of the V formed by said radiating element.

10. A broad band unidirectional end fed dipole V-antenna including a sheet reflector bent to form four legs in the form of a w having two outer legs and two inner legs, a flrst tubular radiating element oriented parallel to a first inner leg of said reflector, the inner end of said first element being open, a first coaxial transmission line with its outer conductor terminating in contact with a first outer leg of said reflector and its inner conductor flared and terminating in contact with the outer end of said flrst radiating element, said inner conductor closing the outer end of said first element, a second tubular radiating element oriented parallel to a second inner leg of said reflector, the inner end of said second element assaosa being open, a secondcoani'a1 traiisn1ission' lin y the outer conductor of said second'lin'e being conductor 'having a first end connected-to the closed end of said first radiating element and a second end connected to the outer conductor of r the intersection of the axes of said radiating elesaid second transmission line adjacent the point of its entry into said second radiating element,

and a third coaxial transmission line connected in parallel with an end of each of said first and said second coaxial transmission lines whereby the direction of maximum response of said'am tenna is in the direction of the apex formed by merits. J Q 1 mu e REFERENCES CITED 1 The following references are of record in the file 01. this patentr V i UNITED STATES PATENTS,"

Number Date Name 2,131,108 Lindenblad Sept. 27, 1938 2,134,126 Hooven Oct." 25, 1938 2,204,175 Carter June 11, 1940 2,210,066 Cork et a1 Aug. 6,1940 2,224,898 Carter Dec. 17, 1940 2,275,646 Peterson Mar. 10, 1942 2,283,620 Alford May 19, 1942 2,419,552 Himmelet a1 "Am- 29,1941 2,434,893 Alford et a1. "Jan. 27, 1948 OTHER REFERENCES Proceedings of the I. R. EQNovember 1940,

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